Transmyocardial revascularization (TMR) is one of several surgical treatments for heart disease. Coronary bypass surgery, balloon angioplasty, and coronary stent placement are well known methods of providing increased blood flow to the heart after the coronary arteries become restricted and occluded as a result of cardiovascular disease. These methods improve the blood supply to the heart. Transmyocardial revascularization takes another approach, and refers to the method of punching, lasing, burning, drilling or coring channels directly into the heart muscle itself, so that these channels may communicate with the intraventricular space. The channels created in TMR may extend across the entire thickness of the heart muscle, or myocardium. For reasons that are not entirely clear, creation of these channels has a clearly beneficial and therapeutic effect on the blood supply to the myocardium. While it is thought that the channels created by TMR permit blood to flow directly from the ventricles into the myocardium, and supply blood to the intramyocardial arteriolar/capillary network, it is not entirely clear that the channels created by TMR must persist and maintain patency (stay open) for a lasting therapeutic effect. It has been surmised that the act of creating the channels stimulates growth of new blood vessels and thus improves blood supply to the part of the heart that is affected by poor blood supply from the coronary arteries.
A variety of devices and methods of performing TMR have been used or attempted. An early use of TMR is discussed in Sen, et al., Further Studies In Acupuncture As A Method A Myocardial Revascularization, 64 Surgery 861 (1968). In this study, TMR was accomplished with biopsy needles, trephines and cannulas. The article discusses a number of other TMR studies, indicating good therapeutic effect at the time.
Aita, Method for Intra-Operative Myocardial Device Revascularization, U.S. Pat. No. 5,380,316 (Jan. 10, 1995) illustrates the use of a laser to burn or lase channels from the outside of the heart, through the myocardium and endocardium and into the endocardial space. The device is illustrated in use in the left ventricle. Aita provides a flexible catheter and a fiber optic waveguide which enables the laser to be applied to the exterior surfaces of the heart through an incision in the chest. In Aita's other work, Aita, Optical Fiber Lasing Apparatus, U.S. Pat. No. 5,093,877 (Mar. 3, 1992), he teaches that laser catheters used inside the arteries should be designed to avoid applying laser energy to the artery walls, and presents a design for a laser lens which purportedly greatly reduces possible perforation of the side wall of the artery. Likewise, Abela, Laser Apparatus For The Recanalization Of Vessels And The Treatment Of Other Cardiac Conditions, U.S. Pat. No. 5,041,109 presents a laser designed specifically to prevent perforation of the blood vessel during use of a laser catheter inside the blood vessel.
Cooley, et al., Transmyocardial Laser Revascularization, 21 Texas Heart Inst. J. 230 (Nov. 3, 1994) discusses the typical case of TMR in which the patient's chest is opened by thoracotomy to expose the heart to a laser. The laser is used to lase channels through the heart and into the left ventricle. The epicardial side of each channel is closed by clotting after hemostasis, or by suturing. In this procedure, the laser pulses were synchronized with the R wave of the patient's EKG, which corresponds to the contraction of the heart muscle. Later evaluation indicated beneficial effect in the treated area of the heart, and some patent channels apparently corresponding to the lased channels.